The present application claims priority from European patent application no. 01830681.1, filed Nov. 2, 2001, presently pending.
The present invention relates in general to the field of conveyors of articles, for instance belt conveyors, chain conveyors and pneumatic conveyors. More specifically, the invention concerns a positioning system of guide elements of a conveyor, such as guide elements for containing, routing, sustaining the transported articles.
In conveyors of articles, systems of guide elements are generally provided for containing and guaranteeing the correct routing of the transported articles in their movement along the transport path; guide elements may also be provided for sustaining the transported articles during their movement. Several typologies of guide elements exist, depending on the type of conveyor they are associated with.
A same conveyor can be employed for transporting articles of different nature, different spatial configuration, or also simply articles of similar nature but of different dimensions.
In order to adapt a conveyor to the transport of different types of articles, for example to assure the correct routing thereof, it may be necessary to adjust the position of the containment guide elements.
Let for example the case be considered of a pneumatic conveyor, of the type widely used for transporting plastic (typically PET) bottles from a production station to a following filling station of the bottles with the desired liquids, drinks or other.
Such a conveyor includes a chamber run through by a high-speed air flow. The chamber extends along a transport path of the bottles, for sections of typical length equal to thirty, forty or even fifty meters.
The chamber is open at the bottom and it is adapted to receive therein the terminal portion of the neck of the bottles. The high-speed air flow running through the chamber, striking the terminal portion of the neck of the bottles, imparts thereto a thrust in the desired direction, determining the movement thereof along the transport path.
In such a movement, the bottles are sustained by a pair of support guides, placed in correspondence of the bottom opening of the chamber and extending parallelly one in front of the other along the transport path. Such support guides act as supports for a support collar projecting from the terminal portion of the neck of every bottle. The bottles are thus transported by the flow of air while being hung to the support guides through the respective support collars.
In the movement along the transport path it is important that the bottles are maintained in a substantially vertical position. This allows avoiding that, because of rockings of the bottles, especially occurring in correspondence of curved sections of the transport path, the support collar stops on the support guides causing undesired stops of the bottle and, consequently, of the whole train of following bottles.
To assure that the bottles are maintained in a substantially vertical position, a pair of lateral containment guides is provided. The containment guides extend parallelly to each other along the transport path, at a lower height with respect to the two support guides. Typically, the two containment guides are placed at a height corresponding to the substantially cylindrical portion of maximum diameter of the bottles.
Generally, the two lateral containment guides are formed by bars of metallic or synthetic material, supported by clamps arranged in longitudinal periodic succession along the guides, for instance at regular intervals of about 50 cm. The clamps are provided with tangs that allow fixing the clamps to respective supports mounted on brackets that, being fixed to the chamber, extend downward therefrom.
To perform their function, the two containment guides must be kept in contact to, or at least they have to graze, the body of the bottles. Clearly, if the two guides are too close to each other, the friction they exert on the body of the bottles may unacceptably scrape the bottle body and even prevent the bottles from moving; on the contrary, if the two guides are too far apart, they cannot prevent the undesired rockings of the bottles.
Since the conveyor has to allow the transport of bottles of different diameter, for instance bottles of 1 lt, 1,5 lt and 2 lt, it must be possible to adjust the position of the two containment guides transversally to the transport path.
To such end, the coupling of the tangs of the clamps to the respective supports is manually adjustable by loosening screws or similar tightening means: acting on these screws loosening them, the tang of the clamp is released. Then, by making the tang of the clamp slide with respect to the respective support, the position of a section of the containment guide can be varied.
To adjust the position of the containment guides, the presence of one or more human operators is needed, which have to adjust the position of every support clamp of the guides. It is easy to realize that this operation is both complicated and extremely long, especially considering that in a transport line of approximately 50 m the number of guide support clamps is of the order of some hundreds. The time required to complete the adjustment operation, that is actually a dead time for the transport line, has a non-negligible impact on the overall manufacturing cost. In addition, the operation is prone to errors that, where not identified before the conveyor is started, can determine an irregular transport of articles, or even the stop of the whole transport line.
As far as the Applicant is aware, a pneumatic conveyor of plastic bottles is known in which the adjustment of the position of the containment guides, rather than being manual, is entrusted to pneumatic actuators. Each support clamp of the containment guides has associated thereto a respective actuator, enabling the movement of the support clamp transversally to the transport path.
It is clear that such a solution, if from one hand eliminates the necessity of a manual intervention for the adjustment of the positions of the guides, thereby reducing the dead times of the transport line, on the other hand impacts substantially on the overall cost of the conveyor and significantly increases the complexity thereof, since several hundreds of pneumatic cylinder-piston assemblies are required.
In addition to this, as in the case of the manual adjustment, it is not guaranteed that all the support clamps are moved of a same distance, with the consequence that the distance between the containment guides is not constant along the transport path. Even worse, it is not possible to assure a synchronous intervention of all the different cylinder-piston assemblies, so that some sections of the guides may move before others sections; the cylinder-piston assemblies may thus experience radial loads that may cause blocking of the pistons.
The cited example of pneumatic conveyor of plastic bottles exemplifies the problems that are generally posed by the operations of setting up a conveyor of articles so as to adapt it to the transport of articles of different nature, spatial conformation or dimensions.
In view of the state of the art outlined, it has been an object of the present invention to provide a positioning system of guide elements of a conveyor of articles that solved the aforementioned problems.
According to the present invention, a positioning system of guide elements of a conveyor of articles according to claim 1 is therefore provided.
Briefly stated, the guide positioning system comprises at least one guide positioning unit comprising a guide positioning element adapted to be operatively associated with a respective guide element for the positioning thereof.
A system of traction-transmitting cables is provided, operatively associated with the at least one guide positioning unit, for transmitting traction forces.
At least one traction unit is additionally associated with the system of traction-transmitting cables for exerting traction forces on the system of traction-transmitting cables.
The at least one guide positioning unit is one among a driven guide positioning unit, wherein the guide positioning element is caused to be moved by the traction forces transmitted by the system of traction-transmitting cables, and a driving guide positioning unit, comprising a motor group associated with the guide positioning element.
The system of traction-transmitting cables comprises, in the case of a driving unit, at least one traction-transmitting cable for transmitting traction forces between the traction unit and the at least one guide positioning unit, and, in the case of a driven unit, at least one first traction-transmitting cable and at least one second traction-transmitting cable for transmitting respective first and second traction forces, respectively causing the guide positioning element to be moved in a first direction and in a second direction.
Thanks to the positioning system according to the present invention, the operations of adjustment of the position of the guide elements of a conveyor are greatly simplified, being rendered substantially automatic. The dead times are therefore drastically reduced, with consequent increase of productivity. Additionally, the risks of committing errors in the adjustment operation are substantially eliminated.